On crop harvesting headers there is generally provided a header frame for mounting on a support vehicle for transport of the header across ground carrying a standing crop for harvesting, a sickle knife mounted across a forward end of the frame for cutting the standing crop, the sickle knife having a row of sickle blades which are movable in a reciprocating action relative to a row of sickle guards, a first drive mechanism for supplying driving rotation to the sickle knife for causing the reciprocating movement of the blades, a crop transfer assembly for transporting the cut crop from the knife along the frame to a discharge opening of the frame and a second mechanism motor for supplying driving rotation to the crop transfer assembly for driving the crop transfer assembly. A mechanical drive input is provided to receive a driving rotation from the vehicle on a suitable output shaft.
In many cases the drive to the transfer assembly and to the sickle knife are mechanical so that simply rotating the input in reverse acts to drive transfer assembly and the knife in reverse directions. This requirement is common in that blockages which occur on a periodic basis can often be cleared by reversing the drives without the necessity of the operator leaving the cab.
Sickle knives include a knife bar carrying a plurality of blades in a row which is reciprocated back and forth so that each blade reciprocates from a position aligned with one guard to a position aligned with the next adjacent guard. In this way the blade effects a cutting action with the side surfaces of the guard as it approaches one guard and then effects a second cutting action with the next adjacent guard as it moves back to its start position.
In regard to the knife, blockages can occur when too much crop enters between the knife blades and stalls the movement of the blades as they approach their cutting action with the guards. In other cases a rigid element can enter between two blades and block the movement of the blades. In both cases it is desirable to reverse the blades away from their stalled position adjacent one guard back away from the guard toward the next adjacent guard. This back-up releases the trapped material allowing it to fall out or at least be pulled out so that the blades can revert to their cutting action with the material removed.
It is in some cases desirable to replace the mechanical drive elements with hydraulic drives so that the mechanical input drives one or more hydraulic pumps which supply fluid to motors driving the knife drive and driving the transfer assembly. In this case the reversing of the mechanical input does not necessarily reverse the motor depending on the type of pumps selected and the circuit arrangement selected.